Delusions of Parasitosis (DP) is a psychiatric disorder in which patients have a false belief that their skin is infested with parasites (lice, fleas, spiders, worms and others). Patients may present to the office with items they believe are infested with parasites. These items may be pieces of skin or other debris in plastic bags, jars, envelopes or in matchboxes. Occasionally, the close contacts of the patient (Spouse, mother, etc) may also believe these delusions; a phenomenon known as "Folie a deux” translated, craziness of two. Apart from these symptoms patients usually have normal personalities and no obvious systemic illnesses.

Delusions of Parasitosis has been associated with psychological disorders such as schizophrenia, obsessive compulsive disorder, bipolar disorder, depression and anxiety disorder, although most patients have only the symptoms if DP. Delusions of parasitosis is more common in Caucasians and tend to occur in females 2:1 over males.

Patients complain of itching, burning, or a crawling sensation under their skin. Skin exam may range from having no lesions to minor scratches to ulcers. Scratching or using erosive chemicals on the skin causes these lesions.

There are no labs to diagnose DP but other causes of itching such as hepititis, HIV, infection, dermatitis herpetiformis, thyroid disease, anemia, renal dysfunction, neurologic dysfunction, and lymphoma must be ruled out. A microscopic exam of skin and hair to rule out scabies and louse infestations can also be done. Amphetamines, methylphenidate and cocaine use should also be ruled out in patients with delusional parasitosis.

Treatment of DP is with antipsychotic medications but this is very challenging because patients do not believe that they have a psychological disorder and therefore compliance becomes an issue. Success of treatment depends on the doctor patient relationship and it is crucial to gain the trust of the patient. The old treatment of choice was pimozide and now it is being replaced with newer agents such as risperidene and olanzapine which has fewer side effects. Many primary care doctors and dermatologists do not feel comfortable subscribing antipsychotic medications, therefore a referral to the psychiatrist may also be considered.

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